I have one I bought at Target that works awesomely. It's as wide as the screen on the 350 and it works with or without a cover on it. I can't find it at target.com right now, or I'd post a picture. It cost 10 bucks though, and I love it so much I'm thinking of buying a few more for future-proofing. I'll post pics if I can find it.
e: here's a picture of one. The lights aren't really blue like they look here, and it's hard to see what's going on with it, but it's basically expandable to fit something up to like 3/4" thick.
Check it:
http://i1134.photobucket.com/albums/.../booklight.jpg